Re: [virtio-dev] Re: [PATCH v3] VIRTIO_F_IO_BARRIER: use I/O barriers in driver

[Jason Wang <jasowang@redhat.com>]

On 2018年06月14日 08:24, Michael S. Tsirkin wrote:
> On Wed, May 16, 2018 at 09:19:44AM +0800, Tiwei Bie wrote:
> > On Tue, May 15, 2018 at 03:39:02PM +0300, Michael S. Tsirkin wrote:
> > > On Thu, May 10, 2018 at 11:41:26PM +0800, Tiwei Bie wrote:
> > > > There will be hardware virtio devices in the future, which
> > > > require drivers to use the barriers suitable for I/O devices,
> > > > compared with software virtio devices which just require
> > > > drivers to use the barriers suitable for CPU cores.
> > > >
> > > > To fix the ordering issue for hardware virtio devices, add
> > > > a new feature: VIRTIO_F_IO_BARRIER. When negotiated, driver
> > > > will use the barriers suitable for I/O devices.
> > > >
> > > > Signed-off-by: Tiwei Bie<tiwei.bie@intel.com>
> > > > Reviewed-by: Stefan Hajnoczi<stefanha@redhat.com>
> > > When you are ready, please open a github issue, then
> > > send Fixes: tag in a response to this mail, asking
> > > to start voting.
> > Got it! Thank you very much!
> >
> > Best regards,
> > Tiwei Bie
> I have a question: an upstream discussion recently
> touched on the subject of need to use bounce buffers
> in special memory, flush cache, or do other tricks
> for DMA.
>
> Do we want to extend this flag to cover that behaviour
> as well? If yes should we rename it and tweak the
> definition? Or should do something else?

Looks not, will device behave differently if we have it?

So it looks to me it was more a platform or software stuffs that could 
be handled by driver itself.

Thanks